Conventionally, in production of packaging containers which contain food; for example, food having fluidity such as tea, juice, soup, or alcohol; i.e., fluid food, a web-like packaging material, a sheet-like packaging material, or the like is used, and the packaging material is formed into packaging containers by means of sealing at predetermined positions through heat sealing, ultrasonic sealing, or a like method. For example, in a filling machine, a web-like packaging material, when used, is formed into a tubular shape; while a strip tape is pressed against the tubular packaging material from inside, the tubular packaging material is sealed in the longitudinal direction by means of a longitudinal sealing device; while being filled with liquid food, the longitudinally sealed tubular packaging material is sealed and cut in the lateral direction at predetermined longitudinal intervals by means of a lateral sealing device, thereby yielding a pillow-like prototype container; and the prototype container is further formed into a predetermined shape, thereby completing a packaging container (refer to, for example, Patent Document 1).
In the conventional filling machine, at a position located downstream of the longitudinal sealing device with respect to the conveyance direction of the tubular packaging material, a pressure roller is rotatably disposed inside the tubular packaging material which has just been sealed in the longitudinal direction, and presses a longitudinally sealed region of the tubular packaging material; and a counter roller is rotatably disposed outside the tubular packaging material in opposition to the pressure roller and receives a pressing force applied by the pressure roller. Accordingly, as the packaging material travels, the pressure roller and the counter roller rotate while pinching therebetween the packaging material and the strip tape, thereby bringing the surface of an overlap of the longitudinally sealed region of the packaging material and the affixal surface of the strip tape into close contact with each other.
Patent Document 1: Japanese Patent Application Laid-Open (kokai) No. 2001-18909